Electronic computer



Nov. 25, 1947.

R. L. SNYDER, JR., ETAL ELECTRONIC COMPUTER Filed March 31, 1942 3 SheetsSheet 2 s IV :s- LE' Enuentors Richard L. Snyder);

Jan 11. yajchman ww ik (mo meg Nov. 25, 1947. i 'R. 1.. SNYDER, JR, EI AI 2,

' ELECTRONIC COMPUTER Filed March 31, 1942 3 Sheets-Sheet 3 6.90. A n/AA uu 14%. I

F1629? N N w, WA A Richard L. sn fi l 8 Jan H.Rajchman.

CAM MIL Ottorneg Patented Nov. 25, 1947 ELECTRONIC COMPUTER Richard L. Snyder, Jr., Glasshoro, N. J., and Jan A. Rajchman, Philadelphia, Pa., assignors to Radio Corporation of America, a corporation of Delaware Application March 31, 1942, Serial No. 437,002

1 Claim. 1

This invention relates generally to computers and particularly to electronic computers for substantially continuously deriving a current or an indication which is a predetermined mathematical function of the variable angular displacement of two elements.

Various mechanical computers have been used heretofore, which utilized trains of cams, gears or other elements for the solution of complex mathematical problems. invention to provide means for deriving electric currents which are characteristic of a desired function of the angular displacement of two mechanical elements, and utilize the currents to actuate an indicator or operating mechanism associated therewith. This is accomplished by light scanning a surface having fiducial marks of predetermined characteristics and arrangement, masking the surface by means of fixed and movable masks to form an aperture having an opening proportional to the angular displacement to be measured, and deriving an electric current by means of a light responsive device associated with the unmasked fiducial marks.

One of the objects of the invention is to provide means for deriving trains of current pulses of a duration which is a function of the variable angular displacement of two elements. Another object is to provide means for scanning an aperture formed by two masking elements, the opening of said aperture being proportional to a function of the angular displacement to be observed, and an electronic device for deriving an indication of the characteristics of the scanned picture.

Another object of the invention is to provide mechanical means for forming an aperture which is proportional to a function of the unknown angular displacement of two elements, scanning said aperture by a light beam, deriving electrical pulses from fiducial marks scanned through said aperture and providing an indication of the number of the electric pulses so derived.

Still another object of the invention is to provide means for deriving electric pulses of frequency and trains of pulses of duration which are a predetermined function of the angular displacement of two elements.

The invention will be described by reference to the drawings of which Figure 1 is an eleva tional view, partly in section, of one embodiment; Figure 2 is an elevational view, partly in section, of a second embodiment; Figure 3 is a perspective view of a third embodiment; Figure 4 is a schematic diagram of a fourth embodiment; Figure 5 is a typical graph of the electric pulses derived It is the purpose of this from the light scanning means; Figure 6 is an elevational view of the aperture forming a por tion of the scanning means of Figure 4; Figure '7 is a modification of the device shown in Figure 6; Figure 8 is a schematic diagram of the circuit which utilizes the pulses derived from these scanning means; and Figure 9 (ag inclusive) is a series of graphs indicating the operating characteristics of the various circuit elements of Fig ure 8. Similar reference numerals are applied to similar elements throughout the drawings.

Referring to Figure l, a motor 5i having shaft 52 rotates the reflector 55 at a substantially constant speed. A fixed cylindrical support 63 having reflecting fiducial marks 64, a fixed mask 66 and a movable mask 85 are disposed about the rotating reflector 55 and concentric with respect to each other. A support 6'! for the movable mask 65 is mounted on a bearing 69 for free adjustment with respect to the fixed mask 66 under control of the handle 68 or other suitable actuating mechanism. A light source 59 associated with a lens 58 is focused through an aperture 51 of the mirror 55 disposed in proximity to the rotating mirror 55. Light from the source 59 passes through the aperture 51', and is reflected from the rotating mirror 55 to the unmasked reflecting fiducial marks 64. Light from the unmasked marks is reflected back to the mirror 55, thence to the stationary mirror 56, and thence to the light responsive device 60, which may be a photocell or electron multiplier, located adjacent thereto. Trains of current pulses derived from the light responsive device 60 are of frequency and duration dependent on the rate at which the unmasked fiducial marks are scanned by the light beam. These trains of current pulses are applied through the switch Hi to either an electronic pulse counter 62 which may be of the type described in an article by H. Lipschitz and J. L. Lawson in the Review of Scientific Instruments. vol. 9, of March 1938, or to the input circuit ID of the frequency measuring circuit described in detail hereinafter and described and claimed in the copending U. S. application of Jan A. Rajchman and Edwin A. Goldberg, Serial No. 437,260, filed April 1, 1942. The contacts 53, 54 are actuated by the rotation of the motor shaft 52. If desired, they may be connected to the electronic counter 62 to reset the counter upon the. completion of each revolution of the shaft.

Figure 2 is another mechanical arrangement for deriving pulses which are a function of the scanning of fiducial marks. The motor shaft 52 drives a flywheel ll carrying the light source'59 and the light responsive device 60 which are connected to slip rings 12 in contact with the brushes 13. A transparent disc I63 having opaque fiducial marks I64 is disposed between the light source 59 and the light responsive device 60 so that when the carrier II is rotated, the light beam between the source 59 and the light sensitive device 60 scans the fiducial marks I64. An adjustable mask I65 which may act in conjunction with a fixed mask attached to the transparent disc I63 I is fixed to the bearing supported on the shaft I6 which is supported by the bearing 15 mounted on the bracket 14. A handle 68 or other actuating device is used for the adjustment of the mask 65 to vary the region of the disc 63 scanned during each revolution of the carrier II. The electric pulses derived from the light responsive device 60 are connected through the slip rings I2 and brushes I3 and the switch 6| toeither an electronic counter or a frequency measuring circuit as described in Fig. 1.

Fig. 3 is a perspective view of a similar means for scanning fiducial marks, in which the mirror I55 is driven, for example, in simple harmonic motion. Light from the source 59 is focused on the mirror I55, reflected therefrom to the fiducial marks 64 on th inside surface of the cylindrical support 63, reflected back to the mirror I55 and thence reflected to the light responsive device 60. A fixed mask 66 and a movable mask 65 can be adjusted with respect to each other to limit the aperature through which the fiducial marks will reflect the light beam back to the mirror I55. It should be understood that the movable mask 65 may be actuated in any desired manner to form an aperture proportional to the angular displacement of the two elements which is to be measured.

Figure 4 is a schematic diagram of a device utilizing a rotating disc 210 having a narrow radial slit 274. A transparent disc 263 having opaque fiducial marks 264, a fixed mask 266, and a movable mask 265 are disposed adjacent the rotating disc 210 and coaxial therewith. Light from the source 59 is interrupted by rotating slit 274 of disc 279 thereby to scan thefiducial marks 264. The relative adjustment of the fixed mask 266 and movable mask 265 determines the angle of the fiducial marks scanned by the rotating light beam. The light beam, after passing through the discs, is directed to the spherical reflector I5 and is reflected therefrom to the light responsive device 60. Electric pulses derived from the light responsive device 60 are utilized in the electronic counter 62 or the circuit of Fig. 8 as described heretofore.

Fig. 6 is an elevational view of the arrangement of the scanning disc, transparent disc having fiducial marks, and the fixed and movable masks of the device schematically shown in Fig. 4. In the device of Fig. 6, the fiducial marks are arranged radially to have equal angular displacement.

Fig. 7 is similar to Fig. 6 with the exception that the fiducial marks are straight lines parallel to a diameter of the disc 263. The arrow indicates the direction of the light beam in scan ing the fiducial marks. Fiducial marks of the type shown, in Fig. 7, will produce light interruptions proportional to the sine of the angular displacement of the fixed and movable masks. The fiducial marks can, of course, be spaced and arranged to provide interruption of the light beam of sequence proportional to any other trigonometric function such as the cosine, tangent, cotangent, secant or cosecant. Likewise,

ing terminal of the resistor the interruption of the light beam can be of sequence proportional to an exponential of the quantity to be measured.

Referring to Fig. 8, the circuit for utilizing the voltage pulses derived from the light responsive .device 60 utilizes a unique arrangement of thermionic tube circuits including a band pass filter, one or more saturation amplifiers, a difierentiating circuit, a peak amplifier, and a novel trigger circuit, as well as means for damping the differentiating circuit and the trigger circuit. These elements are arranged as follows:

The source of voltage pulses, which may include a plurality of frequency components, is applied to the input terminals III of a filter circuit 3 which is designed to pass the frequency band which is to be measured. The output of the filter 9 is applied to the grid circuit of a first thermionic tube I. The grid bias is adjusted to limit the amplitude of the signals to be measured in order to eliminate, as much as possible, response to extraneous signals. The first tube I is operated at the saturation portion of its static characteristic in order to derive an output signal which is substantially of square wave form. The signal is further amplified by a second thermionic tube 2 which is also operated at the saturation point of its static characteristic in order to further improve the square wave form of the signal. The signal of substantially square wave form is next'applied to the input circuit of a third thermionic tube 3. The anode circuit of the third tube 3 includes a two-position switch 20 which is connected in one position to one terminal of a resistor I9 and in another position to one terminal of an inductor I I. The movable arm of the switch 20 is connected to the cathode of a first diode 4 and to one terminal of the capacitor 2I. The remaining terminals of the resistor I9, inductor II and the anode of the diode 4 are all connected through an anode resistor 24 to the source of high potential for the anode of the third tube 3. The remaining terminal of the capacitor 2| is connected to the control electrode of a peak amplifier 5, which is biased to amplify only the voltage peaks of the applied signal. The cathode circuit of the peak amplifier 5 includes a cathode resistor 22. Voltage across this resistor is applied to the cathode circuit of a first trigger tube I. The control electrode of the tube 1 is connected to the anode of a second diode 6, to one terminal of the grid resistor I5, and to one terminal of the capacitor I3. The cathode of the second diode 6 and the remaining terminal of the resistor I5 ar connected to ground. The remaining terminal of capacitor I3 is connected to the anode of the second trigger tube 8 and to one terminal of a resistance network 23. The remaining input terminal of the resistance network 23 is connected to a source of anode potential for the second trigger tube 8. The anode of the first trigger tube 1 is connected to the control electrode of the second trigger tube 8 and to one terminal of a coupling resistor I4. The remain- I4 is connected through the resistor 25 to a source of anode potential for the first trigger tube I.

The operation of the circuit is as follows: The desired frequency component of the signal to be measured is derived from the filter 9 and applied to the control electrode of the first tube I which provides high amplification and, because of its saturation characteristics, clips the peaks of the signal wave. The signal is further amplified'and clipped by a similar action in the second tube 3 and applied as a signal of substantially square wave form to the input of the third tube '3. When the switch 20 is'connected to the inductor ii, the third tube 3 is operated to shock-excite the tuned circuit comprising the natural resonantcharacteristics of the inductor ii, to derive a series of pulses of decreasing amplitude from each square wave pulse applied to the circuit. The first diode 4 provides considerable damping of the pulses of decreasing amplitude to eliminate substantially all of the pulse signal except the first positive cycle. If the switch- 20 is connected to the resistor l9, the resistance capacity network Iii-2| acts as a differentiating circuit, In this network the voltage across the capacitor 2| will be substantially proportional to the rate of change of the square wave signal applied to the network and will therefore include only a sharp positive and negative pulse for each cycle of the square wave signal. When using the differentiating network, the damping diode 4 may be omitted, since it will have little efiect on the circuit operation.

Signals derived from the circuit with either position of the switch 20 are then applied as pulses to the control electrode of the peak amplifier tube 5. If desired, either the inductor II or the resistor i9, and the switch 2i! may be omitted. This tube is biased to clip off and amplify only a positive peak portion of the pulse applied to the control electrode. Sharply peaked voltages from the cathode resistor 22 of the tube 5 are applied to the input circuit of the first trigger tube 1.

The operation of the trigger circuit is as follows: The first trigger tube 1 is biased so that it is normally conducting while the second trigger tube 8 is biased so that it is normally non-conducting. When a positive pulse from the peak amplifier tube 5 is applied to the cathode of the first trigger tube 1, the first trigger tube 1 is biased to cut-oil and the second tube 8 is made to conduct. This condition continues after the exciting pulse has passed, and until the grid of the first trigger tube I, which has been driven to cut-off by the charge on the capacitor i3, becomes sufficiently positive for the first trigger tube 1 to again become conducting and the second trigger tube 8 non-conducting. For a single exciting pulse, the time during which the second trigger tube 8 will become conducting depends upon the capacitance of the capacitor iii, the grid capacitance of the first trigger tube 1, the resistance oi! the resistors I4 and IS, the cut-off voltage of the first trigger tube 1 a well as the rate of change 01 the maximum voltage on the anode of the second trigger tube 8 when the tube is suddenly made to conduct. Since all of these constants can be calculated and fixed, the circuit can be adjusted to any desired time constant.

The limit frequency of the circuit is dependent on the time required for the trigger tubes to return to their normal bias condition after actuation by an exciting pulse. This time interval. may be greatly reduced by the use 01' the second diode 6 which has a damping action on the grid circuit of the first trigger tube 1 by providing substantial attenuation in the circuit when the grid oi the first tube 1 i at positive potential. The action oi the diode 6 also tends to make the duration or the current pulse in the anode circult of the second tube 8 more uniform. The amplitude of this pulse may be maintained at a substantailly constant level by proper voltage reg- .tion amplifier tube l.

ulation of the potentials applied to the trigger tube circuits. The current derived from the output terminals l2 of the resistance network 23 will be a fairly accurate indication of the average rate of occurrence of the exciting pulses applied to the cathode of the first trigger tube 1.

Fig. 9a of the drawing shows a sine. wave signal applied to the input circuit of the first satura- Fig. 9b shows a signal of substantially square wave form derived from the anode circuit of the second tube 2 and applied to the input circuit of the tube 3. Fig. 9c shows the. wave form comprising pulses of diminishing amplitude derived from the tuned circuit i I when the switch 20 is connected to the inductor il. Fig. 9d shows the damping of the pulse current of the first diode 4. The portion of the graph above the dashed line P indicates the positive portion of the pulse current which actuates the peak amplifier 5. Fig. 9e shows the positive pulse derived from across the resistor 22 in the cathode circuit of the peak amplifier 5. Fig. 9a shows the potential variations on the grid of the first trigger tube 1 caused by the application of the pulse shown in Fig. 9e. Fig. 9! shows the corresponding potential variations in the anode circuit of the second trigger tube 8 which are applied to the resistance network 23. The dashed lines in Fig. 9g indicate the damping action of the second diode 6 and clearly show the action of this tube in decreasing the time required for the trigger tubes 1 and 8 to return to their normal bias condition.

It should be understood that the filter 8, tubes i, 2, 3, 4 and 5, or any of them, may be omitted if the signal to be measured has suitable characteristics for the actuation of the trigger circuit comprising the tubes 8, I and 8. It should also be understood that the second diode 6 may be omitted if the operating frequency of the circuit is sufllciently low to permit the trigger tubes I and 8 to return to normal bias condition without the damping action of the diode 6.

We claim:

In a computer for substantially continuouslyderiving a mathematical function 01 the variable angular displacement of two elements, a mirror, a motor for rotating said mirror, a reflector having an aperture therein, a light source associated with said reflector, a fixed cylinder having flducial marks on its inside surface, a movable mask for said fiducial marks, a light responsive device, means for directing light from said light source through said aperture to said mirror thence to said unmasked flducial marks, means including said mirror and said reflector for deriving reflected light from said marks and directing it upon said light responsive device to derive trains of electrical pulses the duration of each said trains being a function of said unmasked marks, and ineans for deriving a signal current of amplitude proportional to the average number of pulses of each of said trains of pulses.

RICHARD L. SNYDER, JR. JAN A. RAJCHMIAN..

REFERENCES CITED The following references are oi record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,176,720 Rayner et al Oct. 17, 1939 7 1,880,105 Reifel Sept. 27, 1932 

